"I was stupidly unaware of the offense this may have caused and the sensitivity around this issue," he recently wrote on Instagram. "I sincerely and unreservedly apologize to all First Nations people for this thoughtless action."For those who think they were owned an apology, it's actually overdue: Hemsworth donned the offensive costume at a New Year's Eve party last year. But now he's apparently more enlightened about how cultural appropriation further marginalizes oppressed communities—like the people at Standing Rock Sioux Reservation.And he's not alone: actress Hillary Duff just apologized for this year's offensive couple costume—Duff and her boyfriend celebrated the holiday this weekend as a Native American and a Pilgrim.

Take Tufts University, where student-leaders of Greek life on campus are particularly worried about costume-related sanctions. They have good reason to be concerned: the university is watching.

"We encourage all students that feel like they have encountered someone who is wearing an inappropriate and offensive costume to please file a report," said Dean of Students Mary Pat McMahon, according to a letter sent to the Greek community. ..

Greek leaders would like to err on the side of caution—how's that for Halloween spirit?—and have asked members of their community to eschew "inappropriate, offensive, and appropriative costumes." Cultural appropriation—dressing up like someone from a different race—is especially frowned upon. But that's not all: costumes "relating to tragedy, controversy, or acts of violence" are also frowned upon.

One wonders what's left. Many students who heed the above guidelines are presumably restricted from dressing up as samurais, hombres, geishas, belly dancers, Vikings, ninjas, rajas, French maids, Bollywood dancers, Rastafarians, Pocahontas, Aladdin, Zorro, or Thor..."